textproduct: Rapid City

KEY MESSAGES

- A ridge of high pressure will continue to support a strong warming and drying trend through Wednesday, with high temperatures exceeding 80 degrees by tomorrow and approaching the low 90s for some on Wednesday.

- A combination of dry fuels, low relative humidities, gusty winds, and the hot temperatures will result in a couple more days of widespread near-critical to critical fire weather conditions through Wednesday. New fires could spread rapidly.

- Isolated dry-leaning thunderstorms are possible Wednesday afternoon and evening. At this time, the primary hazards appear to be lightning and wind gusts in excess of 50 MPH.

- An unsettled pattern returns for Thursday through the weekend with much cooler temperatures. The best chance for windy conditions and rain and snow showers will be Thursday.

DISCUSSION

(This Evening Through Monday) Issued at 154 PM MDT Mon Apr 20 2026

Looking ahead to the next few days, the bulk of the attention will be spent on an incoming low pressure center from the west that will give the area some wild swings in the weather.

For starters, ahead of this incoming low is a very warm ridge. So very warm, well-above normal, temperatures are expected with low temps in the 40s to 50s and high temps in the 80s to 90s tomorrow and Wednesday. South to southeast sustained wind speeds tomorrow, Tuesday, will be around 5 to 15 mph with gusts around 20 mph. Wednesday will see stronger winds with sustained speeds up to 15 to 25 mph with gusts upwards of 30 to 40 mph, strongest winds speeds will be in south-central South Dakota and northeast Wyoming. With relativity humidity values as low as 10 to 15%, fire weather concerns will continue with the greatest concern on Wednesday.

Wednesday will also be a transition day that will usher in some very different weather for the rest of the week. The previously mentioned low pressure center will track eastward through Montana and settle into western North Dakota, giving NE Wyoming and western South Dakota westerly winds and cooler temps beginning Thursday with this new cooler weather lasting into the weekend.

As this new weather settles into the area, some rain showers and thunderstorms are possible late Wednesday into Wednesday night. Higher elevations of the Black Hills could see cold enough air to support snow showers Wednesday night. Stay tuned.

AVIATION

(For the 00Z TAFS Through 00Z Tuesday Evening) Issued At 503 PM MDT Mon Apr 20 2026

VFR conditions are expected through the TAF period.

FIRE WEATHER

Issued At 154 PM MDT Mon Apr 20 2026

Still no relief in the fire weather side of things.

High pressure over the region will support a strong warming and drying trend across northeastern Wyoming and western South Dakota through Wednesday. Daily afternoon relative humidity values will be around the 8 to 20 percent through Wednesday, while temperatures gradually warm into the 80s to near 90. Forecast confidence is also high in absolutely NO meaningful QPF/rainfall through Wednesday evening.

Winds will be marginal and somewhat of a limiting factor at times for meeting formal critical fire weather thresholds, but gusts of at least 25 MPH will likely overlap with these dry humidity values in some areas each day, with much stronger winds regionwide Wednesday (south-southwest at 20-30 MPH gusting 30-40 MPH). The combination of dry fuels/ongoing drought, low relative humidities, gusty winds, and hot temperatures will support widespread near- critical to critical fire weather conditions, with multiple RED FLAG WARNINGS possible over this period. New fires may spread rapidly. Winds today will likely drop off closer to 6 PM, but with continued very dry RHs later into the evening, any new fires that would get started will continue to burn pretty effectively. Overnight RH recovery each night looks to range from as low as 35% in the Black Hills to as high as 40-70% in plains areas early each morning.

In addition to the pattern described above...isolated dry-leaning thunderstorms with primary threats of lightning and gusty erratic downdraft/outflow winds in excess of 50 MPH will be possible late Wednesday afternoon and Wednesday evening almost anywhere, another concern to watch for both fire spread and safety of any fire crews who may be in the field at that time. On the flip side, Thursday is the day to watch for at least SOME potential for wetting rains, which will also coincide with higher humidity and significantly cooler temperatures (although strong NW winds will be possible regionwide). Our current QPF forecast ranges from as low as 0.15 inches along the Nebraska border to as high as 0.35 inches from north of Gillette, across our northwestern South Dakota plans, and along our far eastern counties Thursday, but confidence at this juncture is very low.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning until 8 PM MDT /9 PM CDT/ this evening for SDZ321-322-325-326-332>335. WY...Red Flag Warning until 8 PM MDT this evening for WYZ315-317.